The review is not an indictment of the study design. Murray is a proponent of such trials, and authored a 1998 textbook on the subject, "Design and Analysis of Group-Randomized Trials."
"We're not trying to discourage people from using this design. It remains the best design available if you have an intervention that can't be studied at the individual level," he said.
In analyzing the outcomes of such trials, researchers should take into account any similarities among group members or any common influences affecting the members of the same group, Murray said. However, the review found that the common ground among group members was often not factored into the final statistical analysis.
"In science, generally, we allow for being wrong 5 percent of the time. If you use the wrong analysis methods with this kind of study, you might be wrong half the time. We're not going to advance science if we're wrong half the time," said Murray, who is also a member of the Cancer Control Program in Ohio State's Comprehensive Cancer Center.
The review identified 75 articles published in 41 journals that reported intervention results based on group-randomized trials related to cancer or cancer risk factors from 2002 to 2006. Thirty-four of the articles, or 45 percent, reported the use of appropriate methods to analyze the results. Twenty-six articles, or 35 percent, reported only inappropriate methods used in the statistical analysis. Eight percent of the articles used a combination of appropriate and inappropriate methods, and nine articles had insufficient information to even judge whether the analytic methods were appropriate or not.
The use of inappropriate analysis methods is not considered willful or in any way designed to skew results of a trial, Murray noted.
Murray and his colleagues call for investigators to collaborate with statisticians familiar with group
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